(a)[2]
Use the definitions of speed $v$, frequency $f$ and wavelength $\lambda$ to obtain the wave equation $v = f\lambda$.
(b)
A sound source with frequency $236\,\text{Hz}$ is moving at a steady speed of $20\,\text{m s}^{-1}$. A fixed observer has a microphone connected to a cathode-ray oscilloscope (CRO). As the source travels directly towards the observer, the microphone detects the sound waves. The CRO trace produced is shown in Fig. 5.1. The CRO time-base is set to $1.0\,\text{ms div}^{-1}$.
(b(i))[2]
Calculate the frequency of the sound waves picked up by the microphone.
(b(ii))[2]
Determine the speed of sound in air.
(i)[2]
Calculate the frequency of the sound picked up by the microphone.
(ii)[2]
Determine the value of the speed of sound in air.